Cell adhesion is required for embryonic development, wound healing, and the cell-mediated immune response. The interaction of cells with extracellular matrix or other cells influences their polarity, locomotion, proliferation and differentiation. Cytoplasmic proteins that are co-localized with the adhesion receptors are postulated to contribute to the diverse responses of cells to receptor engagement. Zyxin is a LIM-protein that is concentrated at sites of cell-substratum and cell-cell adhesion. It interacts with proteins involved in actin filament assembly and signal transduction. In addition, zyxin shuttles between the nucleus and adhesive membranes; thus it is an excellent candidate for participating in communication between the nuclear and cytoplasmic compartments. Based on these properties, zyxin is postulated to contribute to adhesion-dependent signaling, a process that is central to normal development and that is disturbed in many diseases including cancer. Here we propose to use biochemical, cell biological, and genetic approaches to probe zyxin function. We will analyze the behavior of fibroblasts derived from mice in which the zyxin locus has been disrupted by homologous recombination. These zyxin (-/-) cells will enable us to perform a structure-function analysis of the zyxin protein. Our preliminary results suggest a role/or zyxin in cell migration and signaling; we will define the molecular mechanism by which zyxin contributes to these processes. We will perform experiments designed to elucidate the nuclear function of zyxin. Finally, we will explore the role of zyxin in development by examining the phenotypic consequences of loss of zyxin function in the mouse and the fruit fly. These studies will provide significant new insight into how cells process information coming from cell adhesion receptors to modulate cell behavior.